From: quai@eps.harvard.edu Date: November 29, 2018 at 8:31 PM Subject: CBET 4577: 20181130 : NEPTUNE Electronic Telegram No. 4577 Central Bureau for Astronomical Telegrams Mailing address: Hoffman Lab 209; Harvard University; 20 Oxford St.; Cambridge, MA 02138; U.S.A. e-mail: cbatiau@eps.harvard.edu (alternate cbat@iau.org) URL http://www.cbat.eps.harvard.edu/index.html Prepared using the Tamkin Foundation Computer Network NEPTUNE A. A. Simon, Goddard Space Flight Center, NASA; and M. H. Wong, University of California at Berkeley; report that they detected a dark spot on Neptune at wavelengths < 600 nm, in images taken with the Hubble Space Telescope (+ WFC3/UVIS) on November 5 UT. This confirms the existence of a dark spot first imaged by WFC3/UVIS on 2018 Sept 10 UT at longitude 335 deg west by the OPAL program (Simon et al. 2015, Ap.J. 812, 55). They provisionally refer to the feature as NDS-2018 (northern dark spot discovered in 2018). NDS-2018 was centered at planetographic latitude 23 degrees north, and was observed at longitude 47 deg west on 2018 Nov 5.56 UT and 97 deg west on Nov 6.35. The width is at least 23 deg of longitude. Longer-wavelength data reveal the continued presence of bright companion clouds associated with NDS-2018, supporting the interpretation that it is an anticyclonic vortex, similar to previous dark vortices (e.g., Smith et al. 1989, Science 246, 1422). The Hubble observing team also includes G. Orton, and A. Hsu. NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2018 CBAT 2018 November 29 (CBET 4577) Daniel W. E. Green